Roel Wieringa Egidio Astesiano Gianna Reggio Alain Le Guennec Heinrich Hußmann Klaas van den Berg Pim van den Broek Is It Feasable to Construct a Semantics for All of UML? What Are the Outstanding Issues? 49-55 1999 conf/ecoopw/1999 ECOOP Workshops db/conf/ecoopw/ecoopw99.html#WieringaARGHBB99